Interactive data projectors create interactive surfaces like those found in physical interactive whiteboards and interactive flat screens, but the coordinate data and even user activation information (touch on, touch off, tip pressed, tip released) are extracted from images by using camera technology located at the projector, instead of using electro-magnetic, optical or acoustical methods embedded into the surface itself. Examples of camera based interactive technology suited for projectors are e.g. disclosed by the present inventor and applicant by WO2001NO00369/US7083100B2 and/or WO2006135241A1/US2009040195A1 using pens with optical patterns which can be tracked by the camera and image recognition system. Other systems are: JP3257585: Visual Science Lab. File: 29 Mar. 1996 Tokuganhei 08-075950) which discloses a camera with IR emitter and a pointing device with reflector, where the camera detects IR and finds out the position of the pointing device, but any synchronization between Camera and Pointing device has not been disclosed. The JP4728540: (Ricoh, File 20 Sep. 2001 Tokugan 2001-287901) discloses a pointing device with some pattern on reflector and a camera which detects a light with the code pattern of the pointing device and find out control information. The JP4037822 (NEC Device Solutions, File: 5 Dec. 2003 Tokugan 2003-407884) discloses a pointing device, which receives a light signal from the camera, and a pointing device that emits a light in response to emitting signal from the camera. The U.S. Pat. No. 6,529,189 (IBM, File 8 Feb. 2000 US09/500194) discloses a pointing device that has IR component and emit a light including control information and camera receives the light.